1. Field of the Invention
The present invention relates to technology for accurately moving a turntable comprising a plurality of disk mounting portions to a scanning position and, more particularly, to a method and an apparatus for controlling the rotation of a turntable which is capable of instantly and accurately moving a disk mounting unit selected by a user to a scanning point regardless of rotation speed variation or aging of parts etc. due to variation of load quantity.
2. Description of the Prior Art
Generally, a disk player is utilized for reproducing data recorded on a disk in video or audio format. However, because all data cannot be recorded on one disk, e.g., when the quantity of data provided to the one disk is too large or the kind of data varies, such as a movie, etc., several disks are required in order to record the data. In this case, a user has to change the disk to record all the data. Accordingly, in order to solve the above-mentioned inconvenience, a disk player is utilized which comprises a disk mounting portion for accommodating a plurality of disks.
FIG. 1 is a plan view illustrating a general turntable which is capable of containing five disks. The turntable 1 comprises an upper surface 1a and back surface 1b. The turntable 1, installed rotatively, comprises five disk mounting portions 2A, 2B, 2C, 2D, 2E at the upper surface 1a in order to mount five disks, and the disk mounting portions 2Axcx9c2E comprise a pickup moving slot 3 in order to make a pickup P movable from a main body unit and irradiate a disk. The disk mounting portion is formed so as to accommodate mountable disks having 8 cm diameter and 12 cm diameter.
A rib 4 for distinguishing each disk mounting portion is placed on the back surface 1b of the turntable by forming a protrusion portion having a certain number of sawteeth at a position of concentric circles of a rotation center of the turntable 1. The rib 4 comprises a plurality of position sensing ribs 4A (the number of position sensing ribs in FIG. 1 is five) for generating different number of pulses at a certain position respectively, and a position sensing auxiliary rib 4B placed among the position sensing ribs 4A in order to generate pulses with a certain interval. Each position sensing rib 4A is formed on a lead position of the each disk mounting portions 2Axcx9c2E on the centering around rotation direction of the turntable 1, and the position sensing auxiliary rib 4B is formed among the position sensing ribs 4A. Accordingly, as depicted in FIG. 3, each position sensing rib 4A for recognizing the first disk mounting portion 2A comprises two ribs 4A1a, 4A1b and a slot 4A2, and the position sensing rib 4A for recognizing the second disk mounting portion 2B further comprises a rib and a slot. And, as depicted in FIG. 3, the position sensing auxiliary rib 4B comprises four ribs 4B1a, 4B1b, 4B1c, 4B1d sequentially among a plurality of auxiliary slots 4B2a, 4B2b, 4B2c. 
In addition, as depicted in FIG. 2, the turntable 1 is installed rotatively on a base 8, and a position sensor 6, including a luminous unit 6A and a light receiving unit 6B, is installed on a printed circuit board placed on the base 8 so as to correspond to the rib 4. When the turntable 1 rotates, because the rib 4 passes between the luminous unit 6A and light receiving unit 6B, the position sensor 6 outputs a high or a low pulse corresponding to a shape of the rib 4, the high or low pulse being provided to a control unit such as a microcomputer through the printed circuit board 7.
Herein, a guide rib 5 having a circular shape is formed on the outer side of the rib 4. A protrusion supporting unit 8A is formed on the base 8 so as to correspond to the guide rib 5 and a felt 9, as a friction member, is fixedly adhered to the protrusion supporting unit 8A. Accordingly, because the guide rib moves along the felt 9, installed on the correspondence surface of the lower part, sag of the turntable 1 can be prevented.
The operation in accordance with the prior art will now be described as follows:
Because the turntable 1 comprises the five disk mounting portions 2Axcx9c2E, five disks can be mounted at the same time. One disk mounting portion selected by a user is rotatively moved to a reproducing position, namely, the scanning position of the pickup P. Accordingly, data recorded on the pertinent disk is reproduced. As described above, in order to retrieve a user select disk among the plurality of disks, original numbers are given to the disk mounting portions 2Axcx9c2E, respectively. A microcomputer (not shown) controls the rotation of the turntable 1 while grasping the present position of the disk mounting portions 2Axcx9c2E by using the circular shaped ribs 4 installed on the backward center of the turntable 1 and position sensor 6, and makes the pertinent disk mounting unit stop at the reproducing position.
In other words, as depicted in FIG. 1, when a motor (not shown) operates and the rotating force is transmitted to the turntable 1, the turntable rotates in the clockwise direction. As depicted in FIG. 2, when the turntable 1 rotates, the rib 4 passes between the luminous unit 6A and light receiving unit 6B of the position sensor 6. Herein, as depicted in FIG. 3, when the rib 4 is placed between the luminous unit 6A and light receiving unit 6B, because light projected from the luminous unit 6A is blocked by the rib 4, the light is not incident to the light receiving unit 6B, and the position sensor 6 outputs a low pulse. However, when a slot is positioned between the luminous unit 6A and light receiving unit 6B, the light is incident to the light receiving unit 6B; and, accordingly, the position sensor 6 outputs a high pulse.
For example, when the turntable 1 rotates in the arrow direction in FIG. 1, the position sensing rib 4A for recognizing the first disk mounting portion 2A passes between the luminous unit 6A and light receiving unit 6B of the position sensor 6, followed by the position sensing auxiliary rib 4B passes. As depicted in FIG. 3, a high pulse 10 is outputted by the position sensing slot 4A2, and three high pulses 12, 13, 14 including a high pulse 11 at a boundary portion are outputted sequentially by the auxiliary slots 4B2a, 4B2b and 4B2c of the position sensing auxiliary rib 4B.
FIG. 5 is a flow chart illustrating a method for controlling the rotation of the turntable in accordance with the conventional art. In order to make the first disk mounting portion 2A stop at a reproducing position, when the motor operates and the rotating force is transmitted to the turntable 1 (step S1), because the slot is one and one high signal occurs when the position sensing rib 4A passes, the microcomputer recognizes the first disk mounting portion 2A (step S2).
Herein, the microcomputer senses the high signal 12 informing the passage of the first auxiliary slot 4B2a of the position sensing auxiliary rib 4B, and cuts off the operating voltage by commanding a stop signal after a certain time Td in order to stop the rotation of the motor (steps S3, S4, S5). According to this procedure, although the driving force of the motor is not transmitted, the turntable 1 rotates more by the rotational inertia force, and stops.
By the same principle, when the position sensing rib 4A for recognizing the second disk mounting portion 2B passes between the luminous unit 6A and lighting unit 6B of the position sensor 6, two high pulses are outputted, and when the position sensing rib 4A for recognizing the fifth disk mounting portion 2E passes therebetween, five high pulses are outputted.
As described above, the microcomputer moves a user select disk mounting portion to a retrieval position by controlling the rotation of the turntable 1 on the basis of the position sensor 6, moving the first disk mounting portion 2A to the retrieval position.
In FIG. 4A, the microcomputer senses the high pulse 10 outputted from the position sensor 6 and the high pulse 11 at the boundary portion by the position sensing rib 4A formed on the lead position of the first disk mounting portion 2A, senses the high pulse 12 in passage of the position sensor 6 of the first auxiliary slot 4B2a of the position sensing auxiliary rib 4B, and cuts off the driving voltage of the turntable driving motor by commanding the stop signal after a certain time from a time when the high pulse 12 is converted into the low pulse.
However, although the driving force transmitted to the turntable 1 is cut off as described above, the turntable 1 stops after rotating by the rotational inertia force.
Accordingly, as depicted in FIGS. 4a and 4c, the stop position of the turntable is set by an experimental method so as to make the second auxiliary slot 4B2b of the position sensing auxiliary rib 4B positioned between the luminous unit 6A and light receiving unit 6B. In other words, a certain time delay Td is set by a trial and error method, the microcomputer senses the high pulse 13 as the second input pulse by the second auxiliary slot 4B2b of the position sensing auxiliary rib 4B, and judges the first disk mounting portion 2A stops at the reproducing position.
However, the rotational velocity of the turntable 1 is differentiated in accordance with the operation state. In other words, the rotation load of the turntable 1 cannot be the same due to the friction force variation between the felt 9 and guide rib 5, the number of installed disks, the surrounding temperature, the humidity, etc., the assembly error of a power transmission means from the motor to the turntable, the dimensional error, etc.
For example, when a load acting on the turntable 1 between an upper limit and a lower limit is called a normal load, as depicted in FIG. 4D, when the first disk mounting portion stops before the second high pulse 13 is inputted by an abnormal load acting on the turntable 1 or by an additional cause, the second rib 4B1b is positioned between the luminous unit 6A and light receiving unit 6B of the position sensor 6, and the low signal occurs, and the microcomputer positions the second auxiliary slot 4B2b of the position sensing auxiliary rib 4B between the luminous unit 6A and light receiving unit 6B of the position sensor 6 by further rotating the turntable driving motor in the clockwise direction.
On the contrary, as depicted in FIG. 4E, when the turntable 1 or first disk mounting portion stops after the second high pulse 13 is inputted due to a load not greater than the normal load which is acting on the turntable 1 or by an additional cause, the microcomputer positions the second auxiliary slot 4B2b of the position sensing auxiliary rib 4B between the luminous unit 6A and light receiving unit 6B of the position sensor 6 by rotating the turntable driving motor in the reverse direction.
When the first disk mounting portion is not stopped at the reproducing position, a damper (not shown) can not be accurately placed at the center of the disk; and, accordingly, it is impossible to perform clamping of the disk.
As described above, in the apparatus for controlling the rotation of the turntable in accordance with the conventional art, because the rotational velocity variation due to the disk weight in accordance with the number of disks installed on the each disk mounting portion, the assembly state of each part, the friction force variation of the felt according to temperature/humidity variation, the rotation load variation due to abrasion of the each part etc. is not considered, it is difficult for the damper to perform the clamping of the disk, and time for operating the turntable driving motor in the clockwise direction or reverse clockwise direction is required until the damper reproduces the select disk after searching the reproducing position. Also, because the product over the normal load in production can not be used, the productivity lowers due to disuse or repair of the product.
Accordingly, the object of the present invention is to provide a method and an apparatus for controlling the rotation of the turntable which is capable of moving a user select disk mounting portion to a targeted position instantly and accurately, regardless of the variation of rotational velocity or the aging of parts due to variations in the load quantity of the turntable.
In order to achieve the object of the present invention, the apparatus for controlling the rotation of the turntable comprises a turntable having a plurality of disk mounting portions which rotates in accordance with the operation of the driving unit, a key input unit for generating a key signal inputted from a user, a sensor unit for generating a pulse signal by a position sensing rib and a position sensing auxiliary rib, a control unit for generating a control signal by a pulse signal of the sensor unit by being inputted by the key signal of the key input unit, and a driving unit for rotating the turntable in accordance with the control signal provided from the control unit.
The method for controlling the rotation of the turntable in accordance with the present invention in order to move a disk mounting portion selected by a key input signal of a user among the plurality of disk mounting portions installed on the turntable to a pickup side, comprises rotating the turntable by supplying the driving voltage to the turntable driving motor, sensing the rotational velocity of the turntable and extracting the output delay time of the driving voltage of the turntable driving motor for stopping the pertinent disk mounting portion at a reproducing position on the basis of the sensed rotational velocity, and cutting off the driving voltage output of the turntable driving motor by checking the pertinent disk mounting portion which approaches the reproducing position and checking the delay time.
In addition, the method for controlling the rotation of the turntable in accordance with the present invention in order to move a disk mounting portion selected by a key input signal of a user among the plurality of disk mounting portions formed on the turntable to a pickup side, comprises rotating the turntable by supplying the driving voltage to the turntable driving motor, varying the output delay time Td of the driving voltage of the turntable driving motor for sensing the rotational velocity of the turntable and stopping the pertinent disk mounting portion at the reproducing position on the basis of the sensed rotational velocity, and cutting off the driving voltage output of the turntable driving motor.